General Information

General Information

1. Silicon and silicone

Silicon and silicone appear to be similar in English, but chemically they mean strictly different things.

Silicon means the dark gray metal silicon represented as the elementary symbol Si, and it is a dark gray metal substance. And the silicone, a high-capacity material, that is essentially used in most industry areas these days, is a unique chemical material having both inorganism and organism, and it means a polymer where such substances as organosilicone and oxygene that have organic components are connected through chemical bonding(Siloxane bonding).

The origin of this name is follows. A.LADENBURG, a silcon scientist saw a hydrolyzed and drained substance as the form of a structure similar to ketone((C2H5)1C=O), that is (C2H5)2Si=O, and named it Silico-Ketone. After that, in 1905, W.DILTHEY identified that the produced drained substance is cyclic, but the name Silico-Ketone was abbreviated as 『Silicone』and was generalized to indicate silicone compounds in general and is being widely used.

2. Silicon and carbon

The molecule backbone is composed of silicon(Si) and oxygen(O), and this makes it fundamentally different from general compound macromolecules.

Carbon(C) and Silicon(Si) belong to group 4 in the periodic table, and as carbon(C) in 2nd period is adjacent to silicon(Si) in 3rd period we can assume that they have similar characteristics. Also, as you can see in the above figure, the 4 bond points of both carbon and silicon are in the shape of a regular tetrahedron with an atom at the center.

However, the element in the 3rd period has an orbital larger by one roll than the element in the 2nd period, which makes the two elements chemically different.
First, compared to carbon whose diameter of covalent bonding is 0.77Å, the diameter of covalent bonding of silicon is 1.17Å, which is about 1.5 times. This diameter of covalent bonding has an absolute influence on the characteristic of the element.

Also, as seen in the table below, the difference in electronegativity also shows the difference in physical and chemical properties such as bond energy. We can see that the electronegativity of silicon is lower than that of carbon and rather close to that of Ge or Sn, metals of the same group, and is likely to receive electrostatic charge in the molecule. Besides, the silicone is different from carbon atom in that silicon has little tendency to make double or triple bondings and has more coordination bond property.

Electronegativity

3. Physical?chemical properties of silicone

One of the most unique characteristic of silicone is its strength to heat and oxidation, which can be explained as the intensity of chemical bonding. As indicated on the right table, we can see that the Si-O bonding, which can be regarded as the backbone of silicone, is larger than that of others, which is partly because its energy level is stabilized as the big difference in the electronegativity of Si and O approximates to ionic bonding.

The fact that the silicone's heat-resistance and oxidation-resistance is good, in other words, the fact that it can be used in high temperature, is one of its important characteristics in practice.

Liquid's surface tension (Temperature: 20 °C)

As the Si-O bonding, unlike pure covalent bonding such as C-C, is in the midway between ionic bonding and covalent bonding, the attraction between the molecules are small, which is why the surface tension of silicone oil is particularly lower than that of other liquids. For the same reason the silicone rubber and silicone oil have excellent cold-resistance, and the low dependence of these various property values on temperature can be regarded as one of the important characteristics in practice.